This invention relates to a machine for drilling or forming tapholes of a shaft furnace. More particularly, this invention relates to a taphole drilling machine intended both for conventional drilling by means of a bit and for carrying out a process in which the closing and opening of the taphole involve the respective operations of introducing a drillrod to a taphole and extracting a drill rod which is left behind in the mass of the taphole between two successive pourings. The drilling machine of this invention includes a mount attached to the free end of a pivoting supporting arm, a carriage sliding along the mount and carrying a working tool, a device for coupling the drill rod to the working tool, and a conical head for guiding and supporting the drill rod.
A drilling machine of the type described, above is disclosed in French Pat. No. 2,494,414 corresponding to U.S. Pat. No. 4,418,894. To make it easier to engage the machine on the drill rod in order to extract it, a support and guide head which diverges frustonconically in the direction of the furnace is provided at the front end of the mount. However, this support and guide head has not proven sufficiently effective when the axis of the work tool, as it approaches the drill rod, is still not entirely in the extension of the drill rod. In most cases, the guide head is even an obstacle to the correct positioning of the drilling machine for the purpose of coupling to the drill rod. Another disadvantage of this prior art machine is that, at the moment when the rod is extracted and before the return of the machine, the frustoconical guide and support head is exposed to jets and splashes of liquid metal, thus causing rapid damage to the head.